(A) Field of the Invention
This invention relates to systems for removing gas and drilled solids from drilling fluids, and more particularly, to a modularized system for centrifugally removing gas and drilled solids from the drilling fluid.
(B) Description of the Prior Art
During the drilling of oil and gas wells, the drilling fluid returned from the bore hole is laden with sand and silt, which are collectively referred to as drilled solids. Additionally, in certain situations, the drilling fluid returning from the bore hole may have entrained therein gas from the drilled formations. Also, some gas in the form of air may be introduced into the drilling fluid through leaks in the mud pumps and the like.
Since the presence of drilled solids and gas in the drilling fluid changes the density, viscosity, and other characteristics of the drilling fluid, it is necessary to remove as much as possible of the drilled solids and gas from the drilling fluid prior to its being recirculated in the well bore.
Numerous apparatus have been developed for removing gas from drilling fluid. Conventional degassers typically operate by either attempting to increase the surface area of the drilling fluid stream or by centrifuging the drilling fluid. The surface area increasing degassers typically include means for spraying or propelling the drilling fluid onto plates or baffles. The impingement of the drilling fluid against the baffles causes bubbles of gas to break out of the drilling fluid and the drilling fluid tends to spread over the baffles and thereby increase its surface area. In centrifugal degassers, the drilling fluid is rotated rapidly in a drum or the like and the gas tends to move inwardly toward the center of the drum and out of the drilling fluid. In both the surface spreading and centrifugal degassers, a sub atmospheric pressure is normally created within the degasser to aid in the removal of the gas. Degassers of both types are typically complicated mechanical devices having numerous rotating impellers or drums and vacuum pumps.
Drilled solids are typically removed from drilling fluids either by settling, screening, centrifuging, or a combination thereof. Settling is the least effective method of drilled solids removal and is therefore usually used only in combination with other methods.
Centrifugal drilled solids separation is normally accomplished with a device including a plurality of hydrocyclones. The drilling fluid is introduced tangentially into the hydrocyclone and clean drilling fluid is discharged from the top and drilled solids are discharged from the bottom. However, the efficiency and effectiveness of hydrocyclone drilled solids removal equipment is deminished significantly by the presence entrained gas in the drilling fluid. The presence of entrained gas causes the drilling fluid to become compressible thereby impeding the operation of the hydrocyclone. Additionally, in certain situations a sub atmospheric pressure is created at the bottom of the hydrocyclone, which tends to draw air into the hydrocyclone thereby gasifying the clean drilling fluid.
It is therefore an object of the present invention to provide an improved system for removing gas and drilled solids from drilling fluids.
It is a further object of the present invention to provide a system for removing gas and drilled solids from drilling fluid that is relatively simple and has a minimum of moving parts.
It is a further object of the present invention to provide a system for removing gas and drilled solids from drilling fluid that effectively degasses the drilling fluid prior to removal of the drilled solids and which does not regasify the drilling fluid during drilled solids removal.